In the scientific and technical literature, sugar-based surfactant molecules are well known. Among them, fatty acid esters of sucrose, sorbitan esters and long-chain alkyl polyglucosides have been widely used in food, personal care and cosmetic or pharmaceutical applications. Some of these surfactants have also been widely used as domestic or industrial cleaning agents or as lubricants.
Despite their widespread use and acceptance, it is well known that ester-based surfactants are only stable over a limited pH range, while alkyl glucosides are stable under alkaline and neutral conditions, but not under strongly acidic conditions.
Other drawbacks are associated with the processes used for obtaining these derivatives. Specifically, in the case of long-chain higher alkyl glucosides, trans-glycosylation is necessary. The use of relatively complicated and expensive facilities is necessary in order to obtain a sufficiently pure product. In the case of sugar-based esters, especially sorbitan esters, expensive and toxic solvents are needed, or high reaction temperatures are then necessary to obtain the products in a sufficiently high yield.
In order to improve the stability under acidic conditions of sugar-based surfactant compounds, a sugar alcohol ether has recently been proposed in WO 2012/148530. This patent application describes a process for preparing polyol ethers in the course of which a mass of molten polyols is reacted with a long-chain alkyl aldehyde under reductive alkylation conditions and acid catalysis. According to this disclosure, difficult and extreme reaction conditions are required, in combination with high-pressure equipment in order to achieve the reductive alkylation reaction. In order to obtain the desired products, an excess of sugar alcohol is judged to be necessary relative to the aldehyde. This leads to large energy consumption per mole of sugar alcohol ether. In addition, at the end of each synthesis, the authors identified by 13C NMR the only compound synthesized (a single regioisomer with an alkyl chain in position 6), for example 2-(2-heptyloxy-1-hydroxy ethyl)tetrahydrofuran-3,4-diol (Example 1), 2-(2-hexyloxy-1-hydroxyethy)tetrahydrofuran-3,4-diol (Example 2) and 2-(2-octyloxy-1-hydroxy)ethyptetrahydrofuran-3,4-diol (Example 3).
Moreover, the prior art describes methods for obtaining monoanhydro-sorbitol. Thus, a method in which sorbitol is dissolved in water in the presence of an acid catalyst and heated under atmospheric conditions for a time sufficient to obtain the maximum content of 1,4-sorbitan is described in Acta Chemical Scandinavica B (1981) page 441-449. Similar processes were also disclosed in which the reaction is performed under reduced pressure (U.S. Pat. No. 2,390,395 and US 2007/173 651) or under moderate hydrogen pressure (US 2007/173 654). In patent application US 2007/173 654, a noble metal cocatalyst is used. However, the isosorbide concentrations measured are quite high, in comparison with the 1,4-sorbitan. Thus, the prior art methods do not make it possible to observe a high yield for the production of monoanhydro-sorbitol under mild reaction conditions.